<div id="mainleft">
    <h2 class="mainleft">Category Product</h2>
    <ul>
        <?php foreach($categories as $category) : ?>
            <li <?php if (isset($current_category->category_id) and $category->category_id == $current_category->category_id) echo 'class="current"';?>>
                <a href="<?php echo site_url($category->category_url)//link den url den url dung site_url ?>">
                    <?php echo $category->category_name ;?>
                </a>
            </li>
        <?php endforeach ?>
    </ul>
    <h2 class="mainleft">search by price</h2>
    <form action="<?php echo site_url('product/search_by_price') ?>" method="get">
        <h2>giá từ:</h2> <input type="text" name="from" /><br />
        <h2>giá đến:</h2><input type="text" name="to"/><br />
        <input type="submit" value="search" />
    </form>
</div><!--end mainleft-->